4 ms·

Can you elaborate on that distribution?

Retric 9y ago
The main causes are altitude/background radiation, temperate, overclocking, faulty parts etc. But, memory can have 100+x the normal failure rates without being particularly noticeable in day to day operations. The value of ECC is often more to detect errors than to correct them. Remember, if you have 10 errors an hour then you unlikely to see them in a 20 second memory test. In practice out of 10,000 machines you might have 1/2 your errors on 10 of them. Critically, if you have ECC memory and you both detect and replace those 10 machines the apparent rate of failures then drops. PS: This is a little dated (09) and only from a single set. But, still an interesting introduction: https://www.cs.toronto.edu/~bianca/papers/sigmetrics09.pdf https://www.cs.toronto.edu/~bianca/papers/sigmetrics09.pdf "Around 20% of DIMMs in Platform A and B are affected by correctable errors per year, compared to less than 4% of DIMMs in Platform C and D. ... About a third of all machines in the fleet experience at least one memory error per year (see column CE Incid. %) and the average number of correctable errors per year is over 22,000. "
- keldaris 9y ago
  As I understand it, the situation is even better (as in, less errors) than that with DDR4. Unfortunately, all the published data I could find is woefully out of date. Still, even if you generously assume something on the order of one correctable memory error per machine year, how many of those errors do you actually care about? Unless you have 100% memory utilization for 24/7 critical tasks, most of those errors probably don't even matter. EDIT: the least out of date reference I could find is a blog post by Jeff Atwood, where he concludes that based on the available literature ECC-correctable errors are quite rare. [1] [1] https://blog.codinghorror.com/to-ecc-or-not-to-ecc/ https://blog.codinghorror.com/to-ecc-or-not-to-ecc/
  - Retric 9y ago
    The median performance for non ECC memory is very good. The problem is worst case performance is hard to detect and much much worse than that. "The median number of errors per year for those machines that experience at least one error ranges from 25 to 611." "We find that for all platforms, 20% of the machines with errors make up more than 90% of all observed errors for that platform." A minority of that 20% again have even more issues. The worse case is literally 10,000x more than 1 bit error per year on a single machine. Without using ECC you really can't tell other than some vague not sure what's wrong just replace it.

The main causes are altitude/background radiation, temperate, overclocking, faulty parts etc. But, memory can have 100+x the normal failure rates without being particularly noticeable in day to day operations. The value of ECC is often more to detect errors than to correct them. Remember, if you have 10 errors an hour then you unlikely to see them in a 20 second memory test. In practice out of 10,000 machines you might have 1/2 your errors on 10 of them. Critically, if you have ECC memory and you both detect and replace those 10 machines the apparent rate of failures then drops. PS: This is a little dated (09) and only from a single set. But, still an interesting introduction: https://www.cs.toronto.edu/~bianca/papers/sigmetrics09.pdf https://www.cs.toronto.edu/~bianca/papers/sigmetrics09.pdf "Around 20% of DIMMs in Platform A and B are affected by correctable errors per year, compared to less than 4% of DIMMs in Platform C and D. ... About a third of all machines in the fleet experience at least one memory error per year (see column CE Incid. %) and the average number of correctable errors per year is over 22,000. "

keldaris 9y ago
As I understand it, the situation is even better (as in, less errors) than that with DDR4. Unfortunately, all the published data I could find is woefully out of date. Still, even if you generously assume something on the order of one correctable memory error per machine year, how many of those errors do you actually care about? Unless you have 100% memory utilization for 24/7 critical tasks, most of those errors probably don't even matter. EDIT: the least out of date reference I could find is a blog post by Jeff Atwood, where he concludes that based on the available literature ECC-correctable errors are quite rare. [1] [1] https://blog.codinghorror.com/to-ecc-or-not-to-ecc/ https://blog.codinghorror.com/to-ecc-or-not-to-ecc/
- Retric 9y ago
  The median performance for non ECC memory is very good. The problem is worst case performance is hard to detect and much much worse than that. "The median number of errors per year for those machines that experience at least one error ranges from 25 to 611." "We find that for all platforms, 20% of the machines with errors make up more than 90% of all observed errors for that platform." A minority of that 20% again have even more issues. The worse case is literally 10,000x more than 1 bit error per year on a single machine. Without using ECC you really can't tell other than some vague not sure what's wrong just replace it.